我有一个TabbedPage,我在其中添加条目,在其他选项卡中我列出了数据。在使用MVVM向数据库添加条目后,如何刷新数据?
的MainPage:
<?xml version="1.0" encoding="utf-8" ?>
<TabbedPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:myMood.Views"
x:Class="myMood.Views.MainPage"
BackgroundImage="logo.png">
<local:Register></local:Register>
<local:Entries></local:Entries>
<local:Statistics></local:Statistics>
<local:Settings></local:Settings>
<local:About></local:About>
</TabbedPage>
条目:
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="myMood.Views.Entries"
Icon="ic_view_headline_white_24dp.png"
xmlns:viewModels="clr-namespace:myMood.ViewModels">
<ContentPage.BindingContext>
<viewModels:EntriesViewModel />
</ContentPage.BindingContext>
<ListView ItemsSource="{Binding MoodEntries}"
HasUnevenRows="True"
Margin="20">
<ListView.Header>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="30*" />
<ColumnDefinition Width="50*" />
<ColumnDefinition Width="50*" />
<ColumnDefinition Width="50*" />
</Grid.ColumnDefinitions>
<Image Source="ic_date_range_black_24dp.png" Grid.Column="0" Grid.Row="0" HorizontalOptions="Center"></Image>
<Image Source="ic_local_hotel_black_24dp.png" Grid.Column="1" Grid.Row="0" HorizontalOptions="Center"></Image>
<Image Source="ic_directions_run_black_24dp.png" Grid.Column="2" Grid.Row="0" HorizontalOptions="Center"></Image>
<Image Source="ic_done_all_black_24dp.png" Grid.Column="3" Grid.Row="0" HorizontalOptions="Center"></Image>
</Grid>
</ListView.Header>
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="30*" />
<ColumnDefinition Width="50*" />
<ColumnDefinition Width="50*" />
<ColumnDefinition Width="50*" />
</Grid.ColumnDefinitions>
<Label Text="{Binding EntryDate, StringFormat='{0:d/M}'}" Grid.Column="0" Grid.Row="0" HorizontalOptions="Center"></Label>
<Label Text="{Binding Sleep, StringFormat='{0:0.0}'}" Grid.Column="1" Grid.Row="0" HorizontalOptions="Center"></Label>
<Label Text="{Binding Stress, StringFormat='{0:0.0}'}" Grid.Column="2" Grid.Row="0" HorizontalOptions="Center"></Label>
<Label Text="{Binding AchivedGoals, StringFormat='{0:0.0}'}" Grid.Column="3" Grid.Row="0" HorizontalOptions="Center"></Label>
<Label Text="{Binding Comment, StringFormat='{0:0.0}'}" Grid.Column="0" Grid.ColumnSpan="4" Grid.Row="1"></Label>
</Grid>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</ContentPage>
视图模型:
using myMood.Models;
using System;
using System.Collections.Generic;
using System.Text;
namespace myMood.ViewModels
{
public class EntriesViewModel
{
public List<MoodEntry> MoodEntries { get; set; }
public EntriesViewModel()
{
MoodEntries = App.MoodDatabase.GetMoodEntries();
}
}
}
注册Viewmodel:
namespace myMood.ViewModels
{
public class RegisterViewModel : INotifyPropertyChanged
{
public MoodEntry MoodEntry { get; set; }
public DateTime LowerLimitDate { get; set; }
public DateTime HighLimitDate { get; set; }
public Command SaveEntry
{
get
{
return new Command(() =>
App.MoodDatabase.SaveMoodEntry(MoodEntry));
}
}
public RegisterViewModel()
{
MoodEntry = App.MoodDatabase.GetMoodEntry(DateTime.Today);
if (MoodEntry == null)
MoodEntry = new MoodEntry();
LowerLimitDate = new DateTime(2018, 1, 1);
HighLimitDate = DateTime.Today;
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
}
答案 0 :(得分:2)
您需要在viewmodel中实现INotifyPropertyChanged
接口。因为当前视图模型不向UI发送数据已更改的信号。
所以你的viewmodel应该是这样的:
public class EntriesViewModel : INotifyPropertyChanged
{
private List<MoodEntry> _moodEntries;
public List<MoodEntry> MoodEntries
{
get { return _moodEntries; }
set { _moodEntries = value; OnPropertyChanged(); }
}
public EntriesViewModel()
{
MoodEntries = App.MoodDatabase.GetMoodEntries();
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}